As a technology for detecting a suspicious person who intrudes into a predetermined area such as a house, a condominium and office to be utilized for crime prevention, a crime-prevention system using a security camera is known (see, for example, Patent Literatures 1 and 2). In such a crime-prevention system, a suspicious person is detected by a person observing an image of the predetermined area photographed by, for example, the security camera, or image recognition processing being performed on the image.
By the way, with related art which uses a security camera, because it is necessary to provide a security camera and an apparatus which records or analyzes a photographed image, it is not easy to introduce the system. Further, a case can arise where a suspicious person cannot be detected because a blind spot of the security camera occurs. It is not preferable to increase the number of security cameras in order to avoid this inconvenience, because it makes a system configuration more complicated and increases cost, which makes introduction of the system further more difficult.    Patent Literature 1: Japanese Patent Laid-Open No. 2014-26506    Patent Literature 2: Japanese Patent Laid-Open No. 2015-138407